The D400 is a newer platform than the D-Premier, the updated D-Premier was the 250. I guess the difference will not be big.
I have compared a D400 with a 250pro (still without CI board) and the 250pro was a clear step up in SQ. So I think that also a 220Pro will be better than a D400 if you have not very demanding speakers. I would not spend the money for going from a 400 to a D-Premier Mono. Try to get a 220/250 pro instead.
Also keep in mind that most D-Premiers are out of guarantee while all pro models still have some years.
I have compared a D400 with a 250pro (still without CI board) and the 250pro was a clear step up in SQ. So I think that also a 220Pro will be better than a D400 if you have not very demanding speakers. I would not spend the money for going from a 400 to a D-Premier Mono. Try to get a 220/250 pro instead.
Also keep in mind that most D-Premiers are out of guarantee while all pro models still have some years.
